Photocatalytic inactivation of Klebsiella pneumoniae by visible-light-responsive N/C-doped and N-tourmaline/palladium-C-codoped TiO2

Klebsiella pneumoniae is considered an emergent human pathogen that can rapidly spread through the public water supply. The frequently used chlorination process for water inactivation has a concern of producing toxic inactivation by-products (DBPs), which in turn lead to secondary pollution after inactivation. At present, the practical use of TiO2 photocatalyst is a developing alternative to water inactivation without DBPs. However, TiO2 is only efficiently activated by UV light. In this study, the performance of visible-light-responsive TiO2 composites (N-TiO2, N-T-TiO2, C-TiO2, and Pd-C-TiO2) in response to photocatalytic inactivation was investigated using K. pneumoniae as a surrogate. The effects of key parameters, including photocatalyst dosage, initial microbial concentration, and light intensity on photocatalytic inactivation, were also evaluated. Light-responsive Modified Hom's (LMH) kinetics was then modeled to characterize the light-absorption capacity of the photocatalyst during photocatalysis. Results indicated that the photocatalytic reaction rate increased with increasing photocatalyst dosage and light intensity but decreased with increasing initial bacterial concentration. Among the photocatalysts, Pd-C-TiO2 showed the highest capacity for bacterial inactivation under visible-light irradiation. For kinetic modeling, the LMH model confirmed the hypothesis that the inactivation rate highly corresponds to the light-absorption ability of the photocatalysts. This study proposes a new LMH model that could be a feasible kinetic approach for predicting powerful photocatalysts that can inactivate waterborne pathogens.